Once in the sea, their sluggish deportment vanishes, and activity is the order of the day. Curiosity aroused, or attack threatened, as Lamont remarks, the herd keep near each other. One moment a crowd of grisly heads and long, gleaming white tusks are above the waves; then follow snorting and hasty breathing; immediately thereafter, a host of brown hemispherical backs, followed by pairs of flourishing hind-flippers, and the lot have dived, again to appear at an interval, and the same performance be gone through. If one gets injured, or a young one is in danger, the host of Walruses close round the boat, grunting, rearing, and snorting, and if their wrath be roused, they rush simultaneously to the fight, and attack the boat. When a young Sea Horse is wounded, the parent becomes desperate, and fearlessly exposes herself, or seizes the youngster under her fore-flipper, and makes off, or defends herself and progeny to the death. There is no security to the hunter on the ice, which the animal in its fury will break through, even when six inches thick. The tusks vary from eight inches to two feet long, and may weigh from five to fifteen pounds; in the males they are generally supposed to be thicker and more divergent. These teeth continuously grow, and, as they wear away, their interior becomes filled with tooth bone. In the young Walrus, there appears to be more teeth than in the adult; but these, as Professor Flower has shown, are exceedingly diminutive denticles, and may or may not remain through life. The first tooth of the molar series in the upper jaw, as in the Dog and other Carnivora, has no predecessor; but the second and third are preceded by milk teeth. In the lower jaw there are three milk teeth.